The invention relates to a braiding machine, in particular a circular braiding machine, for braiding a braiding core that is fed in a permanently continuous or pendulous manner, having at least two braiding thread spools and having a braiding ring that is disposed between the braiding thread spools and the run-on point of the braiding threads onto the braiding core. The braiding threads are guided over the internal surface of the braiding ring.
In braiding machines, in particular in circular braiding machines, braiding cores which have a cross section that is consistent or changes substantially in the longitudinal direction of the braiding core are often fed in order for the component to be produced to be imparted the later shape thereof.
The braiding cores herein can remain in the later component or be released therefrom as a lost core.
Individual threads or else braiding fibers, for example rovings from carbon or glass fibers, can be used as braiding threads.
So-called preforms which serve for the downstream production of diverse components from fiber-reinforced plastics can be made from these braiding threads or braiding fibers by braiding the latter about a braiding core. It is mandatory herein, with a view to high quality of the later components, that the braiding threads or braiding fibers are deposited onto the braiding core as precisely as possible.
In the case of the conventional braiding procedure, the braiding thread spools are received by bobbins which are moved relative to one another on guide tracks such that a braided product is created. The bobbins herein have dissimilar directions of revolving about the braiding core.
In the case of circular braiding machines, the guide tracks are two concentric circular paths that move in opposite directions, the braiding core to be braided moving in the center of said paths so as to be axially offset. It is thus achieved that the braiding threads or braiding fibers of the bobbins in the positive direction of rotation continuously cross those of the negative direction of rotation such that a circular braided product is formed as a braided core is braided.
If braided cores having a complex core geometry are used in the braiding machines, a uniform meshwork structure cannot be achieved by way of the usually round braiding rings with a constant opening cross section.
Differences, which in some instances are significant in terms of the local braiding angle, the layer thickness, and the thread concentration on the individual sides of the braiding core, are created when rigid braiding rings having a round opening cross section are used, even in the case of braiding core cross sections having very dissimilar lateral lengths.
In the case of curved braiding cores, dissimilar braided structures are also created on the internal and the external radius of the curvature when the known rigid braiding rings having a round opening cross section are used.
In order to redress this, DE 10 2010 047 193 A1 describes a circular braiding machine which has a braiding ring made from four angled segments which can all be simultaneously displaced radially toward the braiding core or away from the latter by the same displacement path. The individual segments mutually overlap on the free ends thereof. The adjustment installations engage in the angled region thereof.
This arrangement has the disadvantage that the individual segments of the braiding ring can follow changes in the cross section of the braiding core only when said changes run symmetrically to the longitudinal axis of the braiding ring. Local convexities or concavities, respectively, of the braiding core cannot be followed, such that the quality of the braided product is compromised. Likewise, braiding cores having very dissimilar lateral lengths cannot be braided with adequate quality.
Another solution is known from U.S. Pat. No. 6,679,152 B1. Here, at least one adjustable braiding ring in the manner of an iris aperture is provided in the case of a circular braiding machine. Here too, all segments can only be adjusted simultaneously by the same angular increment. Therefore, it is also not possible for a unilaterally changing cross-sectional shape of the braiding core to be followed with this braiding ring.
It is an object of the present invention to provide a braiding machine using a rigid braiding ring such that the braiding ring opening cross section, both in terms of the circumference as well as of the geometric shape, can be adapted to the respective braiding core cross section.
This object is achieved according to the invention by a braiding machine, in particular a circular braiding machine, for braiding a braiding core that is fed in a permanently continuous manner, having at least two braiding thread spools and having a braiding ring that is disposed between the braiding thread spools and the run-on point of the braiding threads onto the braiding core. The braiding threads are guided over the internal surface of the braiding ring. At least two braiding rings having a constant opening cross section are disposed in series so as to be mutually adjacent in such a manner that the opening cross sections that are delimited by the braiding rings form an overlap opening which corresponds geometrically to the momentary braiding core cross section. The two braiding rings are disposed so as to be individually adjustable.
The invention is based on the concept that the cross section of a braiding core can be represented by at least two rigid braiding rings even when these two braiding rings are positioned such that the opening cross sections thereof are at least partially superimposed such that the overlap opening thus created in terms of geometry approximates most closely the braiding core cross section that is momentarily to be braided. The meshwork structure can thus be kept substantially more consistent, or be influenced in a localized targeted manner, respectively. The overlap opening of the at least two braiding rings can thus be adapted to almost all cross-sectional changes in the braiding core in an optimal manner, and thus guide the braiding threads or braiding fibers, respectively, in an optimal manner. On account thereof, it is possible for the positionally correct run-on point of the braiding threads onto the respective braiding core area to always be guaranteed. Above all, however, the clear spacing between the internal surface of the cross section by overlap and the run-on point can also be minimized at all times. The adaptation of the overlap opening of the braiding rings herein is performed during the braiding procedure.
In particular embodiments, the braiding rings each have an annular opening cross section, an ellipsoidal opening cross section or an ovoid opening cross section. By way of these particularly suitable opening cross sections for the individual braiding rings, the braiding core cross sections that are currently in use today can almost all be fully represented.
In the case of two or more braiding rings being used, the latter can also be disposed so as to nest in one another.
Depending on the braiding core cross section, it is expedient for three braiding rings to be used that, in terms of the opening cross section, are geometrically identical. Each braiding ring herein is separately adjustable such that the opening cross section that is set conjointly by all three braiding rings can be adapted to almost any arbitrary cross section of the braiding core.
In a further aspect of the invention, each braiding ring in the braiding ring plane is disposed so as to be adjustable in a by-axial translatory manner. Still further, each braiding ring may be adjustable by way of a linear guide. A spindle drive that is capable of separate actuation may be provided for adjusting each one of the braiding rings. These aspects of the invention describe an advantageous potential pertaining to how the adjustment of the individual braiding rings can be carried out in a favorable device-related manner. Timing belts can also be used instead of the spindle drive. The individual braiding rings can be actuated in a simple manner by way of the timing belts. This construction is also very rugged.
Apart from a horizontal and vertical adjustability of the braiding rings (x-axis and y-axis), it can moreover be expedient in the case of specific braiding ring geometries for a rotation about the z-axis to be provided when the braiding rings have an opening cross section that deviates from that of an annulus.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.